In the art of supportably mounting a telescopic sight upon the barrel of a firearm various types of supporting brackets have been employed normally in longitudinally spaced pairs which are adapted to supportably engage this telescopic sight and to retainingly engage a portion of the barrel. In the known prior art of record these telescopic sight mounts are adapted to supportably engage a telescopic sight of a single predetermined diameter. Different brackets are required for telescopic sights of different diameters or alternately a sleeve or spacer must be nested within the gripping portions of the brackets in order to mount a telescopic sight of a different diameter. An example of such construction is shown in U.S. Pat. No. 4,026,055.